Patterns of nesting and dung burial in Onitis dung beetles: Implications for pasture productivity and fly control

(1) The nesting biology of Onitis viridulus, O. fulgidus, O obscurus, O. alexis, O perpunctatus, O caffer, O. aygulus, O. tortuosus, O deceptor, O uncinatus, O. picticollis and O. pecuarius was studied in the context of pasture productivity and control of dung-breeding pest flies. The rate and pattern of burial of 1000-g pads were observed at 25 ⚬C for O. viridulus, O caffer, O. aygulus, O. uncinatus and O. pecuarius. (2) O. viridulus and O. pecuarius did not initiate rapid dung burial for up to 9 days after being added to the dung. O. caffer and O aygulus commenced burial within 2-5 days, and maintained a steady daily burial rate of 57-92 g per pair. One pair of O. caffer buried 780 g in 12 days. O. uncinatus buried dung in a stepwise pattern, burying approximately 120 g of dung overnight, with an average of 4 days between burial episodes. (3) O. uncinatus was considered the best species for fly control, since substantial amounts of dung were buried on the first night after pad colonization. O viridulus was considered to be least suitable, since burial did not commence until 6-9 days had elapsed, by which time, at 25 ⚬C, bushfly (Musca vetustissima) or buffalo fly (Haematobia irritans exigua) larvae would have completed feeding and left the dung pad. (4) No bushfly larvae survived in the brood dung of O. alexis, O pecuarius or O. caffer. This was mainly attributed to removal of moisture from brood dung by the beetles, although the apparent low water content of brood dung was partly due to the incorporation of soil into the broods. (5) Species were divided into five groups, based on their nest structure and method of dung burial. The mean depth at which nests were buried in a moist sandy soil ranged from 10 to 103 cm for individual species.